Developing cartridge

Abstract

A developing cartridge includes: a developing roller rotatable about a rotational axis extending in a first direction; a casing configured to accommodate developer therein; an input gear rotatable about a first axis extending in the first direction, the input gear being positioned at one side of the casing in the first direction; a layer thickness regulating member used to regulate a thickness of a developer layer carried on a surface of the developing roller; and an electrode, the electrode having an electrical contact surface. The developing roller has a developing roller shaft extending in the first direction, a covering layer covering a surface of the developing roller shaft, and an elastic layer rotating synchronously with the developing roller shaft, the electrical contact surface is electrically connected to the layer thickness regulating member, and the covering layer is made of a non-metallic material or insulating material.

What is claimed is: 
     
       1. A developing cartridge, comprising:
 a developing roller rotatable about a rotational axis extending in a first direction; 
 a casing configured to accommodate developer therein; 
 an input gear rotatable about a first axis extending in the first direction, the input gear being positioned at one side of the casing in the first direction; 
 a layer thickness regulating member configured to regulate a thickness of a developer layer carried on a surface of the developing roller; and 
 an electrode with an electrical contact surface; 
 wherein the developing roller comprises a developing roller shaft extending in the first direction, a covering layer covering a surface of the developing roller shaft, and an elastic layer rotating synchronously with the developing roller shaft; 
 wherein the electrical contact surface is electrically connected to the layer thickness regulating member, and the covering layer is made of a non-metallic material or an electrically insulating material. 
 
     
     
       2. The developing cartridge according to  claim 1 , wherein the electrical contact surface is positioned at another side of the casing in the first direction. 
     
     
       3. The developing cartridge according to  claim 1 , wherein the covering layer electrically insulates the developing roller shaft. 
     
     
       4. The developing cartridge according to  claim 1 , wherein the layer thickness regulating member abuts an outer surface of the elastic layer. 
     
     
       5. The developing cartridge according to  claim 1 , wherein an electrical resistance between the electrical contact surface and the developing roller shaft is greater than an electrical resistance between the electrical contact surface and the elastic layer. 
     
     
       6. The developing cartridge according to  claim 1 , wherein at least a part of the covering layer is between the elastic layer and the developing roller shaft. 
     
     
       7. The developing cartridge according to  claim 1 , further comprising a supply roller, wherein the supply roller is rotatable about a second axis extending in the first direction, and the electrical contact surface is electrically connected to the supply roller. 
     
     
       8. The developing cartridge according to  claim 1 , further comprising a bracket positioned at another side of the casing in the first direction, wherein the electrode is supported on the bracket, one end of the developing roller shaft is supported on the bracket, and the bracket is made of an insulating material. 
     
     
       9. The developing cartridge according to  claim 1 , further comprising a bracket positioned at another side of the casing in the first direction, wherein the bracket comprises a developing roller bearing thereon, and the covering layer is supported by the developing roller bearing. 
     
     
       10. The developing cartridge according to  claim 1 , further comprising a storage unit, at the one side of the casing, and the storage unit and the covering layer are separated in a second direction different from the first direction. 
     
     
       11. The developing cartridge according to  claim 1 , wherein a through hole is provided at an end of the developing roller shaft. 
     
     
       12. The developing cartridge according to  claim 1 , further comprising an urging protrusion and a storage unit, wherein the storage unit is at the one side of the casing, and the urging protrusion is positioned between the covering layer and the storage unit in a second direction intersecting the first direction. 
     
     
       13. The developing cartridge according to  claim 1 , further comprising a storage unit at the one side of the casing, wherein the electrical contact surface is positioned between the covering layer and the storage unit in a second direction different from the first direction. 
     
     
       14. The developing cartridge according to  claim 1 , further comprising an electrical connector at the one side of the casing in the first direction; wherein the electrical connector is electrically connected to the layer thickness regulating member, and the electrical connector is movable between a first position at which the electrical connector is electrically connected to a grounded metal frame outside the developing cartridge, and a second position at which the electrical connector is electrically disconnected from the grounded metal frame. 
     
     
       15. The developing cartridge according to  claim 14 , further comprising a protrusion, wherein the protrusion is movable according to rotation of the input gear, and the electrical connector moves between the first position and the second position according to movement of the protrusion. 
     
     
       16. A developing cartridge, comprising:
 a developing roller rotatable about a rotational axis extending in a first direction; 
 a casing configured to accommodate developer therein; 
 an input gear rotatable about a first axis extending in the first direction, the input gear being positioned at one side of the casing in the first direction; 
 a layer thickness regulating member configured to regulate a thickness of a developer layer carried on a surface of the developing roller; and 
 an electrode with an electrical contact surface, and the electrical contact surface being positioned at another side of the casing in the first direction; 
 wherein the layer thickness regulating member abuts an outer surface of the developing roller, the electrical contact surface is electrically connected to the layer thickness regulating member, the developing roller comprises a developing roller shaft extending in the first direction and an elastic layer rotating synchronously with the developing roller shaft, and an electrical resistance between the electrical contact surface and the developing roller shaft is greater than or equal to 1 MΩ. 
 
     
     
       17. The developing cartridge according to  claim 16 , wherein the electrical resistance is greater than or equal to 20 MΩ. 
     
     
       18. The developing cartridge according to  claim 16 , wherein the developing roller further comprises a covering layer covering a surface of the developing roller shaft, and the electrical resistance is greater than an electrical resistance between the electrical contact surface and the elastic layer. 
     
     
       19. The developing cartridge according to  claim 16 , further comprising a bracket at another side of the casing, wherein the bracket comprises a developing roller bearing thereon, a surface of the developing roller shaft is covered with a covering layer, the covering layer is made of an electrically insulating material, and the covering layer is supported by the developing roller bearing. 
     
     
       20. The developing cartridge according to  claim 16 , further comprising a supply roller, wherein the supply roller comprises a supply roller shaft, the supply roller shaft is rotatable about a second axis extending in the first direction, and an electrical resistance between the electrical contact surface and the supply roller shaft is greater than 10 MΩ. 
     
     
       21. The developing cartridge according to  claim 16 , wherein a through hole is provided at an end of the developing roller shaft.